Human breast gross cystic disease is a benign breast condition common in adult middle-aged women (Haagensen, Diseases of the Breast, 3rd ed., WB Saunders Publ., pp. 250-266 (1986)). Gross cysts evolve from microcystic apocrine metaplasia, which occurs in the terminal ductal lobular units of the breast (Wellings et al., Hum. Path., 18:381-386 (1987)). The cause of apocrine microcyst transformation into macrocysts is unknown. However, there is evidence that such transformation is a hormonally mediated event. Gross cystic disease first appears in women in their 20's and increases in frequency up to the 40-50 age range, and then essentially disappears as a disease process after menopause (Haagensen, 1986, supra).
Breast gross cystic disease is confirmed by aspiration of cyst fluid. It has been found that as a population, women who have gross cystic disease have an increased risk of developing breast carcinoma (see Jones et al., Brit. J. Surg., 67:669-671 (1980); Harrington et al., Breast, 7:13-17 (1980); Ciatto et al., Eur. J. Cancer, 26:555-557 (1990); Bundred et al., Brit. J. Cancer, 64:953-955 (1991); and Bodian et al., Cancer Det. Prev., 16:7-15 (1992)). The fluid contained within breast gross cysts has been analyzed for a number of components, and has been found to be a unique secretion. The major component proteins have been identified (Haagensen et al., J. Natl. Cancer Inst., 62:239-247 (1979)). One of these component proteins, termed GCDFP-15 for a 15K dalton monomer sized glycoprotein, has been investigated as a marker protein with regard to its circulating blood levels in various clinical situations (see Haagensen et al., 1979, supra; Haagensen et al., 1986, supra, pp. 474-500; and Haagensen et al., Ann. N.Y. Acad. Sci., 586:161-173 (1990)). GCDFP-15 blood levels in "normal"post-menopausal women averages 17 ng/ml.
GCDFP-15 protein has been well characterized with regard to its amino acid structure and the location of its gene on chromosome 7 (see Haagensen et al., 1986, supra; and Myal et al., Somatic and Mol. Genetics, 15:256-270 (1989)). GCDFP-15 is a normal constituent protein of all apocrine gland cells (normal and metaplastic), and of some exocrine glands with apocrine features (serous cells of mandibular salivary glands and the minor salivary glands in the major bronchi) (see Haagensen et al., 1986, supra; Mazoujian et al., Am. J. Pathol., 110:105-112 (1983)). The biological purpose of apocrine cells secreting GCDFP-15 remains obscure. Recent data has shown that breast cell lines exposed to GCDFP-15 in the culture medium results in an enhancement in their growth rate (Cassoni et al., Int. J. Cancer, 60:216-220 (1995)). The protein does have a binding affinity for fibrinogen and is transported in blood bound to fibrinogen (Haagensen et al., 1990, supra). However, no enzymatic effect of GCDFP-15 on fibrinogen has been determined, thus far, and its purpose of binding to fibrinogen has not been established.
The secretion of GCDFP-15 has been shown to be regulated by various hormones both in vivo and in vitro (see Chalbos et al., Cancer Res., 47:2787-2792 (1987); Simard et al., Mol. Endocrinology, 3:694-702 (1989); Dejardin et al., J. Mol. Endocrinology, 7:105-112 (1991); and Haagensen et al., Br. Cancer Res. Treat., 23:77-86 (1992)). Androgens markedly enhance the excretion of GCDFP-15 from both the T47D and ZR75 breast cancer cell lines. The secretory effects of androgens on GCDFP-15 have been shown to be due to increased mRNA synthesis as a primary mechanism (Simard et al., 1989, supra). Differences have been observed between the T47D cells and the ZR75 cells with regard to growth effects of various steroids compared to secretion effects on GCDFP-15. In the ZR75 cell line, a positive correlation has been demonstrated between increased GCDFP-15 secretion and decreased growth rates (Simard et al., 1989, supra). This has been shown in both directions, with androgens slowing growth while increasing GCDFP-15 secretion and estrogens enhancing growth while decreasing GCDFP-15 secretion.
In contrast, with the T47D cell line, androgens have been shown to enhance GCDFP-15 secretion while not appreciably effecting the growth rate (Haagensen et al., 1992, supra). Progestins slow T47D growth rate, while enhancing GCDFP-15 secretion. However, RU486, an antiprogestin, also slowed growth in the T47D cell line while markedly inhibiting GCDFP-15 secretion (Haagensen et al., 1992, supra). Thus, the interaction of various steroids on breast cancer cell lines with regard to GCDFP-15 secretion is complex, but does appear to have androgen-modulated enhancement as a central effect.